Problem 5 - Biology Concepts and Applications

Question

The nutrition of some plants is enhanced by a mutually beneficial association between a root and a fungus. The association is known as a ___________ . a. root nodule b. mycorrhiza c. root hair d. hypha

Step-by-Step Solution

Answer

The association is known as a mycorrhiza.

Step 1: Understand the Meaning of Each Option

To solve the problem, it's important to understand the definitions of all the options provided: - **Root nodule (a):** A root nodule is a swelling on the root of a leguminous plant that contains nitrogen-fixing bacteria. - **Mycorrhiza (b):** A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant that enhances nutrient and water uptake. - **Root hair (c):** A root hair is an extension of a root epidermal cell that increases surface area for absorption. - **Hypha (d):** A hypha is a long, branching filamentous structure of a fungus.

Step 2: Identify Key Characteristics of the Association

The question refers to a 'mutually beneficial association' between a root and a fungus. Symbiotic relationships like this often involve nutrient exchange between organisms where both parties benefit.

Step 3: Selection Based on Description

Based on the definitions, the only option describing a mutually beneficial association involving a root and a fungus is **mycorrhiza (b)**. This relationship helps plants by improving nutrient acquisition and, in return, provides the fungus with carbohydrates.

Key Concepts

Symbiotic Association

A symbiotic association is a relationship between two different organisms where both benefit from the interaction. In the context of mycorrhiza, this relationship involves a partnership between plants and fungi. The fungi attach to the plant roots, and in this cozy setup, both organisms support each other.

• The plant provides the fungus with carbohydrates, which it produces through photosynthesis.
• The fungus, in return, helps the plant absorb essential nutrients, especially phosphorus and nitrogen, from the soil.

A healthy symbiotic association like mycorrhiza can boost a plant’s growth and resilience to environmental stress. It’s a win-win situation in the plant kingdom.

Fungal Root Interaction

The interaction between plant roots and fungi is a fascinating process. When you have a fungus interacting with plant roots, specifically in a mycorrhizal association, there is a lot going on below the ground. The fungi develop structures called hyphae, which are thread-like filaments that extend far into the soil. These hyphae significantly increase the root's surface area, allowing the plant to take in more water and nutrients than it could by itself.

• This expansion is crucial in nutrient-poor soils, where every extra absorption counts.
• The hyphae penetrate the root cells or surround them, forming different types of mycorrhiza, such as ectomycorrhiza, where the fungus surrounds the root, or arbuscular mycorrhiza, where it penetrates the cell walls.

Understanding this interaction showcases the vital role fungi play in supporting plant life.

Nutrient Exchange in Plants

Plants rely on a complex system of nutrient exchange to thrive. In a mycorrhizal association, this nutrient exchange becomes even more efficient due to the symbiotic relationship with fungi. Fungi are adept at breaking down and absorbing nutrients from the soil that plants find hard to access on their own. Once absorbed, these nutrients are transported to the plant and traded for carbohydrates.

• Phosphorus, an element vital for plant growth, is one of the key nutrients that fungi provide.
• With increased phosphorus and other nutrients, plants can perform better in their metabolic functions and are often healthier and more productive.
• The plants contribute to the fungi's needs by supplying simple sugars derived from their photosynthetic processes.

This nutrient exchange serves as a fundamental mechanism through which plants and fungi mutually benefit, ensuring both can survive and prosper in their ecosystems.